This is an EIC Semiconductor Zener Diode, rated at 3W, 56V, in a SMB (DO-214AA) package. It meets the requirements of ROHS for hazardous materials. It is part number 1SMB5943B. It is a device designed to regulate voltage by allowing current to flow in one direction and blocking current in the opposite direction. This enables the device to regulate the output voltage despite fluctuations in the input voltage. It is capable of dissipating up to 3 Watts of power, and is suitable for applications such as circuit protection, voltage regulation, and surge protection.